4 Bicycle Crunch
Sets: As many as needed Reps: 100
Lie on your back and extend one leg and bend the other one so your knee is near your chest. With your hands behind your head, touch your opposite elbow to the close knee. Twist your body and touch the other elbow to your other knee. Perform 100 total reps, doing as many sets as you need to (and resting as needed in between) until you hit that number.